CCE measurements with CCE measurements with Epi-Epi-Si detectorsSi detectors

V. Cindro, V. Cindro, G. KrambergerG. Kramberger, I. Mandić, M. Mikuž, , I. Mandić, M. Mikuž, M. Zavrtanik, M. Zavrtanik,

JoJožef Stefan Institute, Ljubjana, Sloveniažef Stefan Institute, Ljubjana, SloveniaG. LindstrG. Lindström, E. Fretwurst,öm, E. Fretwurst,

University of HamburgUniversity of HamburgV. Konomenkov V. Konomenkov INFN PadovaINFN Padova

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

MotivationMotivation

CCE measurements with heavily irradiated n-type silicon detectors:•50 m epi-Si detectors processed by CiS: 50 cm (p & n irradiated)•75 m epi-Si detectors processed by CiS: 50 cm,150 cm standard and diffusion oxygenated (n irradiated)•150 m epi-Si detectors processed by IRST: 500 cm (n irradiated)

NEW

Why?•to see if the Vfd makes any sense as a relevant parameter at high fluences•to be able to extract trapping times at fluences where TCT fails•to see how much charge can we collect at such high fluences with LHC speed elec.

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

Setup (I) Setup (I)

trigger signal is possible only for electrons passing through diode

~98% purity assures good measurements also at low S/N<1

DAQ chain (rate to disk ~ 50 Hz)•ORTEC 142B preamplifier•custom made shaping amp. (~25 ns)•Tex 2440 oscilloscope connected to PC

Properties•Peltier cooling up to T=-30oC (stable to 0.1oC)•HV (bias) up to 5 kV•Full computer control (automatic scans)

~25 ns

Amplifier+shaper

90Sr

/241 A

mwater cooled heat sink

cold plate

Peltier cooler scintillator

pad detectorTex2440

thermal isolation

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

Setup (II) Setup (II)

pre-amplifier

Cold plate (Peltier cooled)

(water cooled back side)

Source Source support tube

Photo-multiplier+ scintilator

Detector mounting position

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

eq=6x1014 cm

nirr.epi-Si 150 m

Setup (II) - CalibrationSetup (II) - Calibration

Average and most probable signal vs. detector thickness

epi-Sidetectors

Scale calibrated with photons from 241Am (59.6 keV)

Example of energy loss spectraTrigger inefficiency on 2-3% level

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

CV measurements CV measurements

for 50 m thick diodes and 50 cm n irr.From annealing plots -> no SCSI !(introduction rate of donors>acceptors)

for 75 and 150 m thick diodes (150,500 cm)What about the SCSI ?

neutron irradiated

•Vfd(150 m)/Vfd(75 m)~4

•if Neff≠constant it is interesting that the

•additional oxygenation doesn’t help for neutron irradiation

2thicknessV fd

G. Lindström et al.300 min @ 40oC

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

|gc|~7x10-3 cm-1

Measurements performed so far on 50 cm epi-Si detectors show no inversion after neutron irradiation – also for the highest fluence the Vfd rises during “beneficial annealing”

Lower fluences show annealing behavior typical for n type detector !

What about alpha particle measurements?

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

Alpha particle measurementsAlpha particle measurements

75 m thick 50 cm epi-Si detectors after long term annealing (>2 years @20C)!

2.17·1015 cm-2

Vfd=115V

2· 1015 cm-2

Vfd=45V

Difference in field profile

p irradiatedn irradiated

No SCSISCSI during annealing

SCSI after irradiation

75 m diode6·1015 cm-2

Vfd=205V

n irradiatedThe detector is effectively of p-type

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

M.I.P. measurementsM.I.P. measurements

•kink in charge collection plot coincides with full depletion voltage from CV measurements! Also for heavily irradiated silicon detectors the full depletion voltage has meaning•the signal for heavily irradiated sensors rises significantly after Vfd (trapping)•>3200 e for 8x1015 cm-2 neutron irradiated sensor! – more than expected

Vfd is denoted by short line for every sensor!

Epi 150 Epi 75

75 m diodes perform superbly in term of noise (no break downs) also at very high fluences!

T=-10oC

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

M.I.P. measurementsM.I.P. measurements

•At lower fluences the simulation agrees well with data, at higher fluences the simulation underestimates the measurements•What would be the reason? – very likely trapping probabilities are smaller than extrapolated (~ 40-50% smaller)

•Each measurement point was simulated (Vfd, V as for measurements, constant Neff)

•Trapping times taken as “average” of measurements of several groups

•T=-10oC

G. Kramberger, Position Sensitive TCT Measurements with 3D-stc detectors Jun. 25-28, 2006, Prague

ConclusionsConclusions

CCE measurements were performed on new epi-Si detectors (75 and 150 m thick)

•after neutron irradiation the new sensors are effectively of p-type (Vfd annealing, signals)

•at 8x1015 cm-2 the most probable signal of mip for 75 m thick device >3200 e

•the kink in CCE vs. voltage coincides with Vfd ! Vfd is still a relevant parameter at very high fluences!

•The signal is underestimated by simulations at high fluences -> smaller trapping probabilities than extrapolated! At lower fluences the simulation agrees well with measurements.